hard formation meaning in English

坚硬岩层
硬层

Abstract : being aimed at the poor rock - breaking efficiency of rotary water jet in hard formations and deep wells with radial horizontal well technology , by use of powerful advantages of abrasive jet rock - breaking , experimental study on rotary abrasive jet was made
文摘:针对径向水平井钻井技术中旋转水射流在硬地层和深井中破岩能力低的不足，利用磨料射流破岩能力强的优势，对旋转磨料射流进行了试验研究。